1-Alkylcarbapenems are in a sector of the recent topics in the field of chemotherapy. A promising known method for preparing a key intermediate, 4-(alk-2-enyl)-2-azetidinone (IV), is non-stereospecific (e.g., J. Org. Chem., 50, 3438 (1985)) and the stereochemistry of the products can not be controlled to result in poor operability of the process and low yield of the objective 1-alkylcarbapenems.